This invention relates to a process for production of a bleaching clay product from a blend of two or more naturally occurring clay products, each of which has different performance characteristics. Specifically, this invention relates to a process for the production of a blended bleaching clay product by combining a naturally acidic hormite clay, aged or non-aged, with a naturally occurring, less acidic clay product, which contains higher levels of montmorillonite clay. In addition, the invention relates to products produced by these processes.
It is well known that many naturally occurring clays may be used to decolorize oils. These clays decolorize or bleach various oils, such as mineral oils and vegetable oils; various fractions from petroleum, especially lubricating oils, and can be used for refining used lubricating oils, as well as purifying animal fats and beeswax.
In the early 1900""s, it was discovered that the bleaching power of naturally-occurring clays could be enhanced by treating those clays with large quantities of a mineral acid, such as hydrochloric or sulphuric acid, and then washing the acid treated clay free of dissolved salts and residual acid created by the acid treatment. This process is conventionally called acid activation. The general process of acid activation of a clay product includes grinding the clay to a generally uniform, relatively small size, dispersing the clay in water, slurrying the ground clay, and then adding the acid to the clay slurry to form substantially uniform, acid-activated bleaching clay products. This process is disclosed, for example, U.S. Pat. Nos. 1,492,184; 1,781,265; 2,018,987; and 2,671,058.
While many processes are useful for acid activation of various types of clay products, the oils being treated with the acid-activated clay can be damaged if too much acid is utilized during these processes. Because of this adverse effect, it is conventional practice to wash the clay after acid activation to remove any excess acid. However, that washing creates a waste stream containing minerals and acids that are harmful to the environment, which must be neutralized or otherwise disposed of in an environmentally reasonable manner.
U.S. Pat. No. 5,008,226 addressed this issue by limiting the amount of acid that was utilized for activation. Thus, after acid activation, it is claimed that this bleaching clay product need not be washed. This patent teaches the addition of from 1 to 10 percent by weight of concentrated sulfuric acid to certain naturally-occurring, acidic clays containing palygorskite and bentonite. The preferred range of acid addition is between 3 and 5 percent.
A process for producing an acid-activated, decolorizing clay using a naturally occurring, non-acidic clay product is known from U.S. Pat. No. 5,783,511.
Aside from attapulgite clay, bentonite clays can also be activated with acid, but higher concentrations of acid are recommended for activation of bentonite clays than for attapulgite clay. Because of the relatively large amounts of acid used during this acid activation, release of acid by the decolorizing clay to the material being decolorized cannot always be avoided.
A process for acid treatment of an attapulgite clay to produce an improved cat litter is known from U.S. Pat. No. 3,029,783. Relatively low quantities of acid are used in this process, and the acid-treated material is not washed. The material is calcined at 370 to 540xc2x0 C. (700 to 1000xc2x0 F.) before acid treatment, with another calcination at about 400 to 590xc2x0 C. (750 to 1100xc2x0 F.) occurring after the acid treatment. These treatments are necessary to increase the ability of the attapulgite clay to absorb urine and other body fluids. Use as a decolorizing clay is not discussed.
U.S. Pat. No. 1,492,184 describes a process for the activation of crude clay with acid, wherein the acid constitutes not more than 10 percent by weight of the clay. Calcining is expressly avoided to prevent evaporation of the acid.
A process for acid activating a clay is also disclosed by U.S. Pat. No. 4,847,226. In this process, the clay is extruded and ground, and an aqueous acidic solution is added to produce a suspension. The suspension is heated, and the acid-treated clay is separated, washed, filtered and dried. There is no heat treatment of the acid-activated clay. The intent of this treatment is to improve the ability of the clay to filter impurities from liquids. In particular, oil-soluble dyes are said to be removed from oils using this product.
Numerous patents have disclosed acid treatment of various types of absorbent clays. In these patents, the amount of acid that is utilized varies considerably, based on the type of clay utilized and whether the clay is washed after the acid activation step. However, in most circumstances the amount of concentrated acid added exceeds ten percent (10%) by weight. These patents include: U.S. Pat. Nos. 1,844,476; 1,792,625; 1,796,799; 3,617,215; 1,752,721; 1,716,828; 1,455,995; 1,949,673; 2,602,807; 1,544,210; 2,981,697; 1,946,124; and 2,484,828.
Processes for the regeneration of spent acid-activated bentonite clay are disclosed in U.S. Pat. Nos. 5,468,701 and 5,330,946. See also U.S. Pat. Nos. 2,477,386 and 2,671,058.
While these processes are useful, it is still important to produce improved bleaching clay products activated with low percentages of acid which are effective at bleaching various oils.
Accordingly, it is an object of this invention to disclose a process for the production of a blended, bleaching clay product comprised of two or more types of naturally-occurring clay materials, each with different performance characteristics, whereby small amounts of acid are added to the blended clay products.
It is a still further object of this invention to disclose a process for the production of a blended, bleaching clay product comprised of two or more types of naturally-occurring clay materials, which can be effective for the bleaching of certain types of oils, even with no acid activation.
It is a still further object of this invention to disclose a process for the production of a blended bleaching clay product comprised of two or more types of naturally-occurring clay materials, wherein at least one of the clay minerals can be activated by merely aging that clay mineral in situ without adding any acid.
These and further aspects of the invention will be apparent from the foregoing description of the preferred embodiment of the process and the product produced by that process.
One preferred process for the production of a bleaching clay product of this invention comprises selecting a naturally occurring, acidic hormite clay product, selecting a different naturally occurring, clay product with less acidity and higher levels of montmorillonite clay, cleaning the clay products, crushing the cleaned, clay products separately to produce two sets of clay clumps, wherein at least about eighty percent (80%) by weight of the clumps are less than about 2 ins. in diameter, aging the hormite clay clumps for at least about 6 months in situ, blending and drying the two sets of clay clumps together and milling the blended clay clumps to form a bleaching clay product.
An additional preferred process for the production of a bleaching clay product comprises selecting a naturally occurring, acidic hormite clay product, selecting a different naturally occurring, clay product with less acidity and higher levels of montmorillonite clay, cleaning the clay products, blending and crushing the two types of cleaned clay products together to produce blended clay clumps, wherein at least about eighty percent (80%) by weight of the clumps are less than about 2 ins. in diameter, and treating the blended clay clumps with small quantities of concentrated acid. The acid-treated, blended clay product is then dried and milled to form a bleaching clay product. No washing of the bleaching clay product is necessary.
An additional preferred process for the production of a bleaching clay product comprises selecting a naturally occurring, acidic hormite clay product, selecting a different naturally occurring, clay product with less acidity and higher levels of montmorillonite clay, cleaning the clay products, crushing the cleaned clay products separately to produce two sets of clay clumps, wherein at least about eighty percent (80%) by weight of the clumps are less than about 2 ins. in diameter, aging the acidic hormite clay clumps for a period of at least about 6 months, blending the aged hormite clay clumps with clumps of the clay product with less acidity and higher levels of montmorillonite clay, and treating the blended clay clumps with small quantities of a concentrated acid. The acid treated, blended clay product is then dried and milled to form a bleaching clay product.
In addition, the invention includes bleaching clay products produced by these processes.